Circuit for generating pulses

ABSTRACT

A winding inductively coupled to the spark plug wire is connected to the primary of a transformer, the center tap secondary of which is connected to transistor amplifiers, the output of which latter is connected to the input of a monostable multivibrator.

O Umtefi States Patent 1191 [111 3,737,681 Rothermel [4 1 June 5, 1973 54 CjRIjU IT F011 GENE'R'AT Nfi' PULSES 3,490,027 1/1970 Galetto et a] ..330/15 X 3,588,538 6/1971 Picillo; ..307/254 X Inventor: Dieter Rolhermel, 7313 Relchen- 3,109,110 10/1963 Lewis bach, Germany 3,047,736 7/1962 Domhoefer 3,335,290 8/1967 Fischman et a1 ..330/15 X [73] Ass1gnee: Robert Bosch GmbH, Stuttgart, Germany Primary ExaminerJohn W. Huckert 22 i Sept. 29, 1970 Assistant ExaminerJohn W. Huckert Attorney-Michael S. Striker [21] App1.No.: 76,360

[30] Foreign Application Priority Data Oct. 18, 1969 Germany ..P 19 52 604.6 [57] ABSTRACT A winding inductivelycoupled to the spark plug wire [52] 307/246 ggsig g is connected to the primary of a transformer, the [51] nt. Cl. center tap Secondary of which is connected to [58] held of Search ..307/2 2, 246, 254, transistor amplifiers, the output of which latter is com 307/270; 328/67; 330/15; 123/32 EA nected to the input of a monostable multivibrator. [56] References Cited UNITED STATES PATENTS 6 Claims, 1 Drawing Figure 3,148,334 9/1964 Danieisen et al ..328/92- F" i. 1, 3 [9/ W l 1: z: 7

I V f0 19 I 1 i 1/3 6 B! v 5 2 9 i Av II n 11 1 U 1 CIRCUIT FOR GENERATING PULSES BACKGROUND OF THE INVENTION The invention relates to a circuit for generating pulses synchronously with the ignition sparks of an internal combustion engine.

It is often difficult with motor vehicles to start a particular test when the spark plug of a certain cylinder, such as cylinder 1, sparks. When a spark plug sparks, the current rises very quickly from zero to its maximum value in the wire to the plug. The rising current induces a voltage in a pulse generating coil slipped over the spark plug wire. The coil is advantageously wound on a ferrite core. Superimposed on this voltage thus induced is a further voltage that is capacitively coupled from the spark plug cable to the pulse generating wind- SUMMARY OF THE INVENTION An object of the invention is a circuit for producing pulses corresponding to the sparks of a definite spark plug, which circuit is insensitive to interference voltages capacitively induced in the pulse generating winding and is also insensitive to other interfering voltages.

The invention essentially consists of a conductor for the spark-producing current; a pulse generating winding positioned in proximity to said conductor, whereby there is induced in the winding a pulse for each spark; transformer means having a primary winding and a secondary winding, the primary monostable being connected to the pulse generating winding, the secondary winding having a center tap, which center tap is connected to ground; and first and second diode means having each first and second electrodes, the first electrode thereof being connected to the center tap, and the second electrodes thereof being connected to the secondary winding on opposite sides of the center tap, whereby inductively transmitted pulses corresponding to sparks appear on the diodes.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in con nection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING I The single FIGURE shows the circuit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inductive pulse generator, composed of a ferrite core 1 and a winding 2 wound on said core, can be slipped over the spark plug conductor Z, as shown in the FIGURE. The two ends of the winding 2 are connected by a two-wire conductor 3 to respective ends of the primary winding 4 on the ferrite core of a transformer 5. The conductor 3 is provided with grounded shielding 27. A capacitor 6 is shunted across the primary 4. The respective resistors 7 and 9 connect the ends of the primary 4 to a common ground line 8. The primary winding 4 is also advantageously provided with shielding. The described arrangement prevents voltages capacitively coupled to the winding 2 from appearing on the primary winding 4. Since the voltages measured between ground and the two ends of the winding 2 are of equal value and in phase, no capacitively coupled voltages appear on the primary 4. Nonuniform winding of the coil 2 can, however, result in a non-uniform capacitance of the coil 2 with respectto the core 1 or to the spark plug wire Z, which capacitance causes small, capacitively coupled voltages to appear on the primary 4. These voltages, however, are largely short circuited by the capacitor 6. 'The purpose of the resistors 7 and 9 is to prevent any are over between the spark plug wire Z and the coil 2 from charging the primary 4 with respect to ground, and thereby to prevent damage to the two-wire conductor 3 and the transformer S.

The voltage, or pulse, induced in the winding 2, is stepped up by the transformer 5. One end of the secondary winding 10 of the transformer is connected by a resistor 11 to the base of an amplifier transistor 12. The emitter of this transistor and the emitter of a further amplifier transistor 13 are connected to the center tap of the secondary 10, which is connected to the common ground line 8. The base of transistor 13 is connected by a resistor 14 to the otherend of the secondary 10. The emitter-base junction of each transistor 12 and 13 composes a diode. The collectors of the amplifier transistors 12 and 13 are connected together, a capacitor l5 connecting the junction between these two collectors to ground. The pulse induced in the secondary 10 is amplified by these two transistors without being previously rectified. The circuit enables the amplification of even very small voltages induced in the secondary winding 10. The voltage across the capacitor 15 is approximately equal to the battery voltage less the voltage drop across the emitter-collector path of the transistors 12 and 13. The purpose of the resistors 11 and 14 is to reduce the small capacitively coupled interference voltages to such a low value that they cannot turn on the transistors 12 and 13.

Despite the amplification provided by the transistors 12 and 13, the pulse signal across the capacitor 15 is plifier stage having the transistors 16 and 19. The emitter of the amplifier transistor 16 is connected by resistor l7 and a diode 18 to the base of the other amplifier transistor 19, the collector of which is connected by a capacitor 20 to ground and the emitter of which is connected to a resistor 21 to a positive line 22 and by a capacitor 23 to ground. A capacitor 24 is connected between the emitter and collector of the transistor 16.

The signal appearing across the capacitor 15 is conducted to the control electrode, or base, of the amplifier transistor 16, which is connected as an emitter follower. The purpose of the capacitor 24 is to bypass small interfering voltages that are superimposed on the pulse signal appearing across the capacitor 15. The transistor 19 is connected by a common emitter. The purpose of the capacitor 23 and the resistor 21 is to prevent interference, conducted through the current supply, from reaching the emitter of transistor 19. The diode l8 prevents voltages that are smaller than the potential barrier of this diode from being conducted to the base of the transistor 19. The purpose of capacitor 20 is to bypass any interference voltages which may reach the collector of transistor 19.

Inasmuch as ignition produces two signals a first, when the current in the spark plug wire Z rises to its peak value at the beginning of the sparking; and a secend, when the current in the wire Z dies awayit can occur that two signals will be conducted to the primary winding 4. In order to ensure that an output signal appears only at the beginning of the sparking in other words, only while the current is increasing in the wire Z the output of transistor 19 is connected to a monostable multivibrator 25. The construction and operation of a monostable multivibrator is so well known that the multivibrator 25, except for the following remarks, will not be described. The time constant (the time required for the multivibrator to return to its original state) must be longer than the period of time required for the current in wire Z to rise to its maximum value and then to die away. If thereappears on the collector of transistor 19 a pulse voltage caused by the rising current in wire Z, the monostable multivibrator 25 is triggered to its other state. During a pulse caused by the declining current in wire Z, the multivibrator-2S has not yet returned to its original state, so that the latter pulse cannot affect the multivibrator. Consequently,

there appears on the output of the terminal 26 only one pulse for each spark of the spark plug, on the wire of which latter the core 1 and winding 2 are mounted.

The circuit described is a simple solution to the problem of generating a pulse in synchronism with the ignition sparks of a particular cylinder. The circuit is highly immune to the various kinds of interferences that motor vehicles commonly generate.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits differing from the types described above.

While the invention has been illustrated and described as embodied in a circuit for generating pulses, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adaptit for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this 1 invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. An arrangement for monitoring the generation of ignition sparks in an internal combustion engine by monitoring the flow of ignition current through an electrical conductor of a component in the ignition system of such internal combustion engine, comprising, in combinatioma pulse generating winding adapted to be slipped over said electrical conductor to generate a voltage pulse upon the flow of ignition current through said conductor; transformer means having a primary winding and a secondary winding, said primary winding being connected to said pulse generating winding, said secondary winding having a center tap and said center tap being connected to ground; and first and second transistors each having first and second electrodes forming a base-emitter junction, said first electrodes being connected to said center tap and said second electrodes being each connected to a respective end of said secondary winding, said first and second transistor having collectors connected to each other; first capacitor means connecting said collectors to to ground; first and second resistor means connecting one of said second electrodes to a respective end of said secondary winding and operative for reducing the strength of capacitively coupled interference voltages to values insufficient to turn on said transistors; third and fourth amplifier transistors each having an output electrode and a control electrode; second capacitor means connecting the output electrode of said third transistor to groud for bypassing interference voltages superimposed upon said pulse; and diode means connecting the output electrode of said third transistor to the control electrode of said fourth transistor.

2. A circuit as defined in claim I, wherein said fourth transistor further includes a third electrode, and including current supply means for the circuit; additional resistor means and third capacitor means respectively connecting said third electrode to positive and to ground for preventing interference from being conducted through said current supply means to said third electrode; and monostable multivibrator means having an input connected to said fourth transistor output electrode, the time constant of said monostable multivibrator means beinglonger than the duration of the ignition current.

3. A circuit as defined in claim 2, including capacitor means connecting said fourth transistor output electrode to ground for bypassing interference voltages appearing on said output electrode of said fourth transistor.

4. An arrangement for monitoring the generation of ignition sparks in an internal combustion engine by monitoring the flow of ignition current through an electrical conductor of a component in the ignition system of such internal combustion engine, comprising, in combination, a pulse generating winding adapted to be slipped over said electrical conductor to generate a voltage pulse upon the flow of ignition current through said conductor; transformer means having a primary winding and a secondary winding, said primary winding being connected to said pulse generating winding, said secondary winding having a center tap and said center tap being connected to ground; and first and second transistors each having first and second electrodes forming a base-emitter junction, said first electrodes being connected to said center tap and said second electrodes being each connected to a respective end of said secondary winding; and further including respective resistor means connecting each end of said primary winding to ground for preventing charging of said primary winding with respect to ground in the event of arc over between said electrical conductor and said pulse generating winding.

5. A circuit as defined in claim 4, including capacitor means shunting said primary winding for shorting out capacitively coupled interference voltages that might otherwise appear on said primary winding.

6. A circuit as defined inclaim 4, including conductor means for electrically connecting said pulse generating winding to said primary winding, and grounded shielding means for shielding said conductor means. 

1. An arrangement for monitoring the generation of ignition sparks in an internal combustion engine by monitoring the flow of ignition current through an electrical conductor of a component in the ignition system of such internal combustion engine, comprising, in combination, a pulse generating winding adapted to be slipped over said electrical conductor to generate a voltage pulse upon the flow of ignition current through said conductor; transformer means having a primary winding and a secondary winding, said primary winding being connected to said pulse generating winding, said secondary winding having a center tap and said center tap being connected to ground; and first and second transistors each having first and second electrodes forming a base-emitter junction, said first electrodes being connected to said center tap and said second electrodes being each connected to a respective end of said secondary winding, said first and second transistor having collectors connected to each other; first capacitor means connecting said collectors to to ground; first and second resistor means connecting one of said second electrodes to a respective end of said secondary winding and operative for reducing the strength of capacitively coupled interference voltages to values insufficient to turn on said transistoRs; third and fourth amplifier transistors each having an output electrode and a control electrode; second capacitor means connecting the output electrode of said third transistor to groud for bypassing interference voltages superimposed upon said pulse; and diode means connecting the output electrode of said third transistor to the control electrode of said fourth transistor.
 2. A circuit as defined in claim 1, wherein said fourth transistor further includes a third electrode, and including current supply means for the circuit; additional resistor means and third capacitor means respectively connecting said third electrode to positive and to ground for preventing interference from being conducted through said current supply means to said third electrode; and monostable multivibrator means having an input connected to said fourth transistor output electrode, the time constant of said monostable multivibrator means being longer than the duration of the ignition current.
 3. A circuit as defined in claim 2, including capacitor means connecting said fourth transistor output electrode to ground for bypassing interference voltages appearing on said output electrode of said fourth transistor.
 4. An arrangement for monitoring the generation of ignition sparks in an internal combustion engine by monitoring the flow of ignition current through an electrical conductor of a component in the ignition system of such internal combustion engine, comprising, in combination, a pulse generating winding adapted to be slipped over said electrical conductor to generate a voltage pulse upon the flow of ignition current through said conductor; transformer means having a primary winding and a secondary winding, said primary winding being connected to said pulse generating winding, said secondary winding having a center tap and said center tap being connected to ground; and first and second transistors each having first and second electrodes forming a base-emitter junction, said first electrodes being connected to said center tap and said second electrodes being each connected to a respective end of said secondary winding; and further including respective resistor means connecting each end of said primary winding to ground for preventing charging of said primary winding with respect to ground in the event of arc over between said electrical conductor and said pulse generating winding.
 5. A circuit as defined in claim 4, including capacitor means shunting said primary winding for shorting out capacitively coupled interference voltages that might otherwise appear on said primary winding.
 6. A circuit as defined inclaim 4, including conductor means for electrically connecting said pulse generating winding to said primary winding, and grounded shielding means for shielding said conductor means. 